|Publication number||US6561024 B2|
|Application number||US 09/789,264|
|Publication date||May 13, 2003|
|Filing date||Feb 20, 2001|
|Priority date||Feb 20, 2001|
|Also published as||US20020112551|
|Publication number||09789264, 789264, US 6561024 B2, US 6561024B2, US-B2-6561024, US6561024 B2, US6561024B2|
|Original Assignee||Sauer-Danfoss, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (13), Referenced by (2), Classifications (10), Legal Events (5)|
|External Links: USPTO, USPTO Assignment, Espacenet|
Measuring the rotational speed of a shaft is a need for many customers of hydraulic/hydrostatic pumps and motors. One method of doing this is to affix a ring to the shaft, or something rotating with a constant ratio to shaft, that has several equally spaced magnetic poles. A Hall Effect sensor can then be placed in proximity to the magnetic ring. The Hall Effect sensor can detect the rate at which the magnetic poles pass by, providing enough information to calculate the rotational speed of the shaft. The applications of this technology are many, including engine speed and ground speed. A challenge that exists when assembling the hydraulic/hydrostatic pump or motor is to accurately and consistently place the sensor at the correct location, related to the magnetic ring. If the sensor is too close, it may come in contact with the ring during operation due to shaft deflection, tolerance issues, or other reasons. This may cause damage to the sensor, the magnetic ring, or both parts. If the sensor is placed further away, the magnetic field created by each pole on the magnetic ring will be weaker, reducing the Hall Effect and making the sensor less accurate, especially at high rotational speed. If the sensor is to work correctly, therefore, correct placement is crucial
In most applications, the Hall Effect sensor is placed in a threaded housing, then screwed into the pump or motor's external housing until the desired clearance is reached. Unfortunately, this assembly procedure is a blind operation, meaning that it is impossible to directly measure the clearance. One way to establish the correct distance is to screw in the sensor until it touches the magnetic ring, then unscrew it a defined number of rotations (based on thread pitch). This process relies heavily on operator knowledge and skill.
It is therefore a principal object of this invention to provide a method and means of creating a clearance or free space between two parts under blind assembly conditions.
A further object of the invention is to provide a method and means of creating a clearance or free space between two parts under blind assembly conditions which is fast and accurate to implement.
These and other objects will be apparent to those skilled in the art.
A method for creating a finite clearance space between two parts under blind assembly conditions involves threading an elongated sensor into a housing containing the part to be sensed by first placing a spacer element on an operative surface of the sensor wherein the spacer element has a radial thickness equal to the finite clearance space. The sensor is screwed unto the housing in a radial direction towards the operative surface of the sensor until the spacer element engages the operative surface, thereby specifically locating the operative surface a precise radial distance from the operative surface.
To resolve the placement issue, this invention applies a material to the end of the sensor that has thickness equaling the optimum distance between the magnetic ring and the sensor. With this insert, operators are no longer required to unscrew the sensor to establish an acceptance distance. The sensor can simply be screwed in until the applied material (spacer) touches the item being sensed. The spacer is not a functional part of the sensor, so if it contacts the ring during operation, causing part or all of it to wear away, there are no adverse consequences.
FIG. 1 is a sectional view through a motor housing showing a sensor and an object to be sensed with a spacer element of this invention in its operative position; and
FIG. 2 is an enlarged scale view of portion 2—2 of FIG. 1.
FIG. 1 shows a conventional hydrostatic motor housing 10 which rotably contains a rotatable cylinder block 12 which has a plurality of movable pistons 14 which are spring-urged towards swashplate 15. Each piston has an outwardly extending ball 14A which is rotatably received in coupler 14B. The cylinder block drives the output shaft 15A. During assembly, a speed sensing ring 16 of the type shown in U.S. Pat. No. 5,325,055 is rigidly secured to block 12. Ring 16 has an outer peripheral surface 18 which is the surface to be sensed.
The housing 10 has a threaded aperture 20 with a radial axis 22 which intersects the center axis 23 of block 12. A Hall Effect sensor 24 with a threaded shoulder 26 which is threadably mounted in aperture 20. Sensor 24 has an operating probe 28 and a sensing surface 30 on its inner end. (FIG. 2). The predetermined design of the apparatus determines that the optimum radial distance between the sensing surface 30 and the peripheral surface 18 of ring 16 has a radial magnitude of A (e.g., 0.030 in.).
A disposable spacer element 32 is secured to the sensing surface 30 of sensor 24 and has a predetermined thickness of A. Spacer element 32 is secured to surface 30 of sensor 34 in any convenient manner before the sensor is threaded into aperture 20. The diameter or area of the probe 28 and spacer element 32 must be less than the diameter of the shoulder 26 and the aperture 20 so as to permit the entry thereof through aperture 20. The material of sacrificial spacer element 32 should be non-magnetic, and should be firm but capable of eroding upon the rotation of ring 16. A suitable material is Syntheseal® N-8094 made by Interface Solutions, Inc. Any suitable adhesive (e.g. MACbond 18-1192 made by Mactac of Stowe, Ohio) can be used to affix spacer element 32 to surface 30. The radial thickness of spacer element 32 is typically only a few thousandths of an inch (e.g., 0.030 inches).
In operation, the sensor 24 is screwed into aperture 20 until spacer element 32 engages the outer peripheral surface 18 of ring 16. The operator will then cease screwing the sensor 24 into the aperture 20. The matching threads on shoulder 26 and in aperture 20 will normally hold the sensor 24 in place. A nut or fastening means (not shown), on sensor 24 can also be used for this purpose. This process will locate the surface 30 the predetermined radial distance A from the outer surface 18 of ring 16. The block 12 within housing 10 can then be operated and rotated, and the sensor 24 will be accurately positioned with respect to speed ring 16 even though assembly of the sensor 24 was done under “blind” conditions. The erosion of sacrificial spacer element 32 will take place harmlessly.
It is therefore seen that this invention will accomplish its stated objectives.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US3418456 *||Dec 14, 1966||Dec 24, 1968||Monarch Marking Systems Inc||Encoded tag reader|
|US3981194 *||Aug 21, 1975||Sep 21, 1976||William O. Lehman||Flow meter system|
|US4017756 *||Aug 18, 1975||Apr 12, 1977||Borg-Warner Corporation||Automatic sensor positioner|
|US4401282 *||Aug 4, 1981||Aug 30, 1983||Nissan Motor Co., Ltd.||Emergency locking seat belt retractor|
|US4655689||Sep 20, 1985||Apr 7, 1987||General Signal Corporation||Electronic control system for a variable displacement pump|
|US4717322||Aug 1, 1986||Jan 5, 1988||Toyota Jidosha Kabushiki Kaisha||Roots-type fluid machine|
|US4922197||Aug 1, 1988||May 1, 1990||Eaton Corporation||High resolution proximity detector employing magnetoresistive sensor disposed within a pressure resistant enclosure|
|US5325055||Dec 11, 1991||Jun 28, 1994||Sauer, Inc.||Retained magnetic strip for mounting on a rotating member to provide a magnetic flux to be sensed|
|US5351555||Jul 29, 1991||Oct 4, 1994||Magnetoelastic Devices, Inc.||Circularly magnetized non-contact torque sensor and method for measuring torque using same|
|US5850046 *||Oct 31, 1996||Dec 15, 1998||Bently Nevada Corporation||Transducer mounting bracket and verification device: apparatus and method|
|US5936397||Dec 12, 1996||Aug 10, 1999||Siemens Aktiengesellschaft||Sensor device for determining rotational speed and/or direction of a rotor shaft and mounted onto the rotor shaft with a resilient securing part|
|DE3515436A1 *||Apr 29, 1985||Oct 30, 1986||Achenbach Buschhuetten Gmbh||Measuring device for determining the position of the piston in a hydraulic piston-cylinder unit for adjusting the rolls in a rolling mill|
|GB2348933A *||Title not available|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US6959598||Feb 3, 2004||Nov 1, 2005||Emerson Electric Co.||Liquid level sensor for appliance and associated method|
|US20050166671 *||Feb 3, 2004||Aug 4, 2005||Peterson Gregory A.||Liquid level sensor for appliance and associated method|
|U.S. Classification||73/431, 73/637, 73/866.5, 73/494|
|International Classification||G01P3/488, G01D11/00|
|Cooperative Classification||G01P3/488, G01D11/00|
|European Classification||G01P3/488, G01D11/00|
|Apr 26, 2001||AS||Assignment|
Owner name: SAUER-DANFOSS INC., IOWA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:BELL, AARON;REEL/FRAME:011709/0773
Effective date: 20010212
|Oct 27, 2006||FPAY||Fee payment|
Year of fee payment: 4
|Dec 20, 2010||REMI||Maintenance fee reminder mailed|
|May 13, 2011||LAPS||Lapse for failure to pay maintenance fees|
|Jul 5, 2011||FP||Expired due to failure to pay maintenance fee|
Effective date: 20110513